Map of life expectancy at birth from Global Education Project.

Wednesday, January 11, 2006

Darwin was Wrong

Or rather, his knowledge was incomplete. Bacterial evolution doesn't only work in the standard Darwinian mode -- mutation and natural selection. By various mechanisms, bacteria can exchange genes across species. They can do this by a kind of interspecies sex -- live cells contacting each other and swapping genes on small pieces of DNA called plasmids; by actually leaving DNA around when they die and their cell walls disintegrate, DNA which can be absorbed by other bacteria; and through the action of viruses.

This creates a major problem for us humans. Bacteria sometimes cause problems for us, and we want to kill them. I've written about bacterial drug resistance before, of course, but I want to get into a bit more deeply right now. The best introduction to the issue that I have found is this Scientific American article by Stuart Levy (PDF, rather badly scanned, I'm afraid), who also heads up the Alliance for the Prudent Use of Antibiotics at Tufts.

There's a lot of concern right now about pandemic flu -- and if you enjoy being scared, I recommend you visit Effect Measure where the apocalyptic flu thing is getting the full run down. That is indeed worth worrying about, but if we do experience The Big One soon it will be a transient event. It will sweep through the global population, kill some number of tens of millions of people and cause substantial economic disruption, and then it will be gone. The population will have immunity to that particular strain of influenza and we'll get back to what passes for normal these days. Antibiotic resistant bacteria, however, are a continual, and growing problem. In the worst case, if pathogenic bacteria that we have no way of controlling become pervasive in the environment, it will become impossible to do surgery safely; minor injuries could be fatal; people will lose limbs, eyes, internal organs, to infections that are readily treatable today.

This is not, however, a matter of fate. It is entirely a function of human greed and folly. The problem does not arise simply because we treat bacterial infections. That alone, if done properly, creates little risk of creating widespread antibiotic resistant bacteria. Because maintaining the genes that confer resistance imposes some metabolic cost on bacteria, if antibiotics are not present in the environment, there will be selection pressure against the genes and they will become scarce in bacterial populations. The danger arises when antibiotics are continually present.

For that reason it is difficult to prevent antibiotic resistance in hospitals, where continual, heavy use of antibiotics is unavoidable. Resistant nosocomial infections will probably continue to cause trouble for the foreseeable future, although people are working hard to reduce the problem. But of greater concern is the presence of resistant strains in what epidemiologists call the community, which means every place that isn't a health care facility. These arise because antibiotics are routinely fed to livestock in feedlots; sprayed on fruits and vegetables; and because people take antibiotics that they don't actually need, and don't finish courses of antibiotics even when they are prescribed appropriately. Remember that resistant genes are dangerous even when they occur in non-pathogenic organisms, because these "good germs" can pass them on to pathogens.

And that brings us to another, growing problem, the proliferation of anti-bacterial everything and anything for the home. Consumer products companies market antibacterial bathroom soap, kitchen cleaners, toys, high chairs, car seats, doggie toys, even clothing. Bacteria can evolve resistance to the agents used in these products, which confers cross resistance to some antibiotics. These products are essentially useless -- you can't possibly make your home sterile, nor would you want to. There is no evidence that they protect people against infections, either.

The advice is the same as you got from your grandmother. Wash your hands frequently with ordinary soap and warm water. Clean your clothing and bedding in hot water. Dry it in the dryer, or hang it in the sun. Keep your house clean, with water and detergent. Wash your fruits and vegetables, cook your meat thoroughly. Don't buy any of that junk. Don't ask your doctor for antibiotics, let her figure out if you really need them. And, politically, we need to work to limit use of antibiotics in agriculture.

Listen up folks! This is really, really important. If you're worried about dying and stuff, it's far more important than the War on Terrorism™. Really.

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